The long term goal of the applicant is to determine the development of the regulatory proteins of coagulation during normal and abnormal gestation in order to understand the clinical hypercoagulability of the sick preterm infant. This information will be important to predict and prevent thrombotic complications in newborn infants requiring intensive support. The specific aim of this proposal is to utilize unique resources available at the University of Colorado Health Sciences Center including unusual long-term fetal ovine (sheep) catheterization preparations and well developed ovine models of normal, diabetic, hypoglycemic, growth retarded, twin, acute and chronically hypoxic gestations in order to answer the following questions about the fetal development of the protein C (PC) system. 1) Do the molecular forms or activities of fetal PC differ from results found in the neonatal lamb or the mature sheep? 2) When in gestation are PC and its cofactor protein S (PS) expressed in fetal ovine plasma? 3) What is the developmental rate of rise of these proteins? 4) Is the developmental rate of rise of levels of PC and PS in normal ovine gestation regulated by increases in the level of mRNA for PC and PS within fetal hepatocytes or placental cells? 5) How do specific gestational complications affect plasma level and molecular forms of PC and PS, activity of PC and levels of mRNA for Pc and PS? In order to answer these questions, risk fetal sheep. These samples will be assayed for levels of PC and PS antigen, molecular forms of PC and PS as well as function of PC. In addition, liver and placental tissue will be obtained at several gestational ages of pregnant ewes and their fetal and neonatal lambs in order to determine normal developmental levels of hepatic and placental mRNA for PC and PS. Methods proposed for assay of PC and PS include rocket immunoelectrophoresis and ELISA for determination of antigen level, Western blotting for molecular forms as well as chromogenic and clotting assays of PC function. Levels of tissue mRNA will be determined by Northern and Slot Blot technique. This data will be compared with data collected in a identical fashion from high risk gestations. This proposal represents an exciting opportunity to study the fetal development of the PC system and will yield valuable information because of our unique resources in Perinatal Medicine and fetal physiology, coagulation biochemistry, and molecular biology.